Now, in a first-of-its-kind experiment, researchers from Harvard are preparing to release calcium carbonate into the stratosphere in 2019 — a small-scale trial that could provide crucial data about the potential risks and rewards of a larger-scale geoengineering effort.

Sun Blockers

The Harvard experiment will operate at a tiny scale, according to Nature. The researchers will send a steerable balloon up into the stratosphere, where it’ll release about 100 grams of calcium carbonate. Calcium carbonate, which is the active ingredient in antacids, is a tempting candidate for geoengineering efforts because simulations show that it could stay in the air for years as it reflects sunlight.

After releasing the calcium carbonate, the balloon will use a laser imaging system to watch how the particles disperse — data the researchers can use to model how larger quantities of the substance might behave.

Stratos-Fear

Critics say that geoengineering efforts are Band-Aid solutions that treat the symptoms of climate change instead of the cause: global carbon emissions. Jim Thomas, the co-executive director of an environmental advocacy organization called the ETC Group, told Nature that he fears the Harvard project could push the concept of geoengineering into the mainstream.

But advocates say that anything that could buy some extra time in the face of looming climate catastrophe is worth exploring.